Fluke 8842a AC Calibration AT Other Frequencies, Optimizing USE of the 5450A, Tolerance

Maintenance 6

CALIBRATION

If ERROR 41 occurs, the most likely cause is that the reference input is incorrect (e.g., has the wrong polarity). If the input is in fact correct, refer to the Troubleshooting heading in this section.

1.

2.

3.

Table 6-13. Tolerance Limits

CALIBRATION

A/D Calibration

Offset and Gain Calibration

VDC, mA DC

Ohms

VAC, mA AC

HF AC Calibration

TOLERANCE

±244 counts from prompt

±488 counts from prompt ±3002 counts from prompt ±3002 counts from prompt ±9999 counts from prompt

6-21. AC CALIBRATION AT OTHER FREQUENCIES

For special applications where the 8842A is to be used to measure ac voltages or currents exclusively at a single frequency or narrow range of frequencies, accuracy may be enhanced at that frequency (or range of frequencies) by performing calibration according to the following procedure. Note that this may degrade the accuracy at frequencies significantly removed from the frequency of optimization.

To optimize performance at a frequency less than 1 kHz, perform the offset and gain calibration procedure, above, using the frequency at which measurements will be made rather than 1 kHz. This technique may be used for both the VAC and mA AC functions. At the calibration frequency, the 8842A will yield accuracy closely approaching the specified mid-band performance.

To optimize performance at a frequency greater than 1 kHz, perform calibration as follows:

1.Perform the Offset and Gain Calibration procedure using inputs at 1 kHz.

2.Perform the High-Frequency AC Calibration procedure using inputs at the desired frequency of optimization rather than at 100 kHz. Skip step 5 in that procedure

3.Again perform the Offset and Gain Calibration procedure, this time using inputs at the desired frequency of optimization rather than at 1 kHz.

6-22. OPTIMIZING USE OF THE 5450A

If the Fluke 5450A Resistance Calibrator is used to calibrate the 2-wire ohms function, the following procedure is recommended to optimize the calibration of the lowest two ranges. (The 5450A has a 25 mΩ "floor" which would otherwise result in 25 digits of error in the 200Ω range of the 8842A.) In this procedure, the 8842A is referred to as the unit under test (UUT).

1.Complete Offset and Gain Calibration for the UUT’s 4-wire ohms function. The UUT will then be taking verification readings.

2.Connect the UUT to the 5450A as shown in Figure 6-4.

3.Select the "SHORT" from the 5450A, and measure this value at the 5450A OUTPUT terminals using the UUT in 4-wire ohms. If in remote, take the average of four

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